Hi Thomas, bricksbuilder.io is currently still running a very old version of Bricks (we are currently working on a new website) and accordingly should not be used as a reference
I can’t reproduce the problem on your site with a simple reload because the font file is already in the cache. If I clear the cache during the reload, it is reloaded, and at that moment, the default font is visible for a split second, which is unavoidable.
It is recommended to use a similar default fallback font, e.g., Arial if you use a sans-serif font, so that you don’t switch from a serif to a non-serif font.